The ability to simultaneously communicate analog and digital signals through a communications channel is known. In one prior art technique, the voice and data signals are typically transmitted either via frequency-division multiplexing or time-division multiplexing. In frequency-division multiplexing, the data channel and the voice channel are allocated different sub-bands of the channel's bandwidth. Examples of that are U.S. Pat. Nos. 4,757,495, 4,672,602, and 4,546,212. In time-division multiplexing arrangements, voice signals are sampled, digitized, and interleaved with digital data to form a single information stream which is communicated over the available channel. Practically every digital carrier system (e.g. the T1 carrier system) is an example of that. In another prior an technique set forth in U.S. Pat. No. 4,512,013, issued Apr. 16, 1985, something akin to frequency division multiplexing is used to attain simultaneous voice and data half duplex operation. Finally, most recently, in a pending patent application entitled "Technique for Modulating Orthogonal Signals with One or More Analog or Digital Signals", Ser. No. 08/076526, filed Jun. 14, 1993, assigned to the present assignee, and incorporated herein by reference, the ability to simultaneously send voice and data or either voice or data alone through a communications channel in a nonmultiplexer manner using a generally coextensive frequency band is disclosed.
With any of the foregoing techniques, a modem interconnects an associated telephone and data terminal equipment (DTE) to other remote telephones and DTEs via a communications link. This link is typically pan of the public switched telephone network (PSTN). In any event, there is a need for the modem to appropriately interact with its associated telephone and DTE for incoming calls. For incoming calls, such interaction involves providing an off-hook signal to the communications link and ringing the phone for voice calls, or appropriately forwarding the incoming data to the DTE or a combination of both of these functions. One prior art technique for providing this interaction for a communication simultaneously coupling voice and data requires that the communication be established by using an application program which activates a modem's autodialer. The users at each end of the communications link are expected to be "standing by" and upon noting the receipt of incoming data via the applications programs can pick up their respective telephones. Obviously, this procedure requires that the communications be prearranged. In addition, the communications program has to staff as a data call with voice communications being subsequently added.
While the foregoing methodology works satisfactorily, it is not suitable for many communications users who use their voice and data communications equipment in a completely arbitrary, unscheduled, and unplanned manner. It would therefore be desirable if a technique could be devised wherein a modem would interact with its associated voice and DTE in a manner compatible with such usage.